Generating Method and Device, Receiving Method and Device for Dual-Frequency Constant Envelope Signal with Four Spreading Signals

ABSTRACT

The application relates to a generating method and device, receiving method and device for a dual-frequency constant envelope multiplexed signal with four spreading signals. According to the method, the four baseband spreading signals s 1 (t), s 2 (t), s 3 (t), s 4 (t) can be modulated to a frequency f 1  and a frequency f 2  respectively, so as to generate the constant envelope multiplexed signal on a radio carrier frequency f p =(f 1 +f 2 )/2, where the signals s 1 (t) and s 2 (t) are modulated on the frequency f 1  with carrier phases orthogonal to each other, the signals s 3 (t) and s 4 (t) are modulated on the frequency f 2  with carrier phases orthogonal to each other, f 1 &gt;f 2 . The method comprises: determining a power ratio allocated to the four baseband spreading signals s 1 (t), s 2 (t), s 3 (t), s 4 (t) in the constant envelope multiplexed signal; storing an additional phase lookup table, wherein the table includes additional phases of an in-phase baseband component I(t) and a quadrature-phase baseband component Q(t) of the constant envelope multiplexed signal; obtaining an additional phase θ of a segment of the current time by looking up the additional phase lookup table; and generating an in-phase baseband component I(t) and a quadrature-phase baseband component Q(t) of the constant envelope multiplexed signal, and generating the constant envelope multiplexed signal S RF (t) based on the obtained additional phase θ.

TECHNICAL FIELD

The application relates to the field of satellite navigation, and morespecifically, generating method and device, receiving method and devicefor a dual-frequency constant envelope signal with four spreadingsignals.

BACKGROUND

With the development of Global Navigation Satellite System (GNSS), therequirement of navigation services is increasing. The number of signalstransmitted on the same frequency band by the navigation satellitesystems is growing, which aggravates the crowding of the already limitedfrequency band available for the satellite navigation. With growing inthe number of signals broadcast in the same frequency band by anavigation system, the complexity of the satellite payload keepsincreasing.

It is desired to multiplex signals on two different frequencies tocertain specific requirements in the system construction and applicationfor, e.g., the smooth transition of the adjustment in the centralfrequency of signal during the system update and upgrade, ortransmission of multiple groups of service information with contentscomplimentary to each other onto two very adjacent frequencies, etc.Moreover, under the condition that the transmitting power from satelliteis limited, in order to keep enough receiving power at the receiver end,it is desired that the high power transmitter on the satellite have ashigh power efficiency as possible. Thus, it is required that the HighPower Amplifier (HPA) on the satellite keep working in the non-linearsaturated region. However, when the HPA works near the saturated point,if the input signal does not have a constant envelope, the outputcomponents will be subject to such distortions as amplitude modulation,amplitude-phase conversion, and so on, which will cause the amplitudeand phase distortion in the transmitting signal and seriously affect theperformance of the receiving end. Therefore, it is required to ensurethat the combined signal has constant envelope.

As a typical instance, AltBOC (U.S. patent applicationUS2006/0038716A1), a constant envelope modulation technique, is appliedin the signal on E5 band of European Galileo navigation system. InAltBOC, two sets of BPSK-R(10) signals respectively modulated on twoseparated carrier frequencies with 30.69 MHz away from each other (E5a:1176.45 MHz, E5b: 1207.14 MHz) are combined into a constant enveloped8PSK signal with central frequency at 1191.795 MHz. By such technique,advantageously, the number of signal transmitters carried as the payloadof satellite is saved, and a wideband multiplexed signal is constructed,such that the receiver supports not only the narrowband receivingstrategy by which the signal components on E5a and E5b are separatelyreceived and processed, but also the wideband receiving strategy bywhich the integral multiplexed signal in its full band is received for abetter ranging performance. However, in AltBOC, the four signalcomponents to be multiplexed must have equal power, which restricts theflexibility in application of the technique. As known in the GNSS, sinceranging is the primary purpose of GNSS signal, it tends to allocate morepower on the pilot channel than the data channel in the GNSS signalstructure design, in order to promote the accuracy and robustness ofpseudorange measurements and carrier phase tracking. Moreover, theadoption of different spreading code chip waveforms by signal components(such as BPSK-R, sine-phased BOC, cosine-phased BOC, TMBOC, QMBOC, etc.)results in the different performance in acquisition, tracking and datademodulation at the receiver end. Therefore, it is required to provide adual-frequency constant envelope multiplex technique for GNSS signalswhich is more flexible than AltBOC, in particular, such that the fourcomponents can be different in power allocation and the spreading codechip waveform of different signal components can be flexibly selected.

PCT international patent application no. PCT/CN2013/000675, with thetitle of “Satellite Navigation Signal and Generation Method, GenerationDevice, Receiving Method and Receiving Device Therefor”, discloses amethod for generating a multiplexed signal with constant envelope basedon the values and power ratio of four signal components to bemultiplexed. According to this method, the in-phase baseband componentand quadrature-phase baseband component of the multiplexed signalsatisfying the requirement for constant envelope can be calculated.However, the calculation of the in-phase baseband component andquadrature-phase baseband component of the multiplexed signal in asatellite navigation signal generating device will result in theincrease of the complexity in implementing the device.

SUMMARY

The purpose of the present application is to provide a generating methodand device, receiving method and device for a dual-frequency constantenvelope signal with four spreading signals, which can at leastpartially address the issues in the prior art.

According to an aspect of the present application, a method forgenerating a dual-frequency constant envelope multiplexed signal withfour spreading signals is disclosed, in which the four basebandspreading signals s₁(t), s₂(t), s₃(t), s₄(t) are modulated to afrequency f₁ and a frequency f₂ respectively, so as to generate theconstant envelope multiplexed signal on a radio carrier frequencyf_(p)=(f₁+f₂)/2, where the signals s₁(t) and s₂(t) are modulated on thefrequency f₁ with carrier phases orthogonal to each other, and thesignals s₃(t) and s₄(t) are modulated on the frequency f₂ with carrierphases orthogonal to each other, f₁>f₂, wherein the method furthercomprises:

-   -   determining a power ratio allocated to the four baseband        spreading signals s₁(t), s₂(t), s₃(t), s₄(t) in the constant        envelope multiplexed signal;    -   storing an additional phase lookup table, wherein the table        includes additional phases of an in-phase baseband component        I(t) and a quadrature-phase baseband component Q(t) of the        constant envelope multiplexed signal, and the table is        configured by dividing a subcarrier period T_(s) of the baseband        spreading signal into multiple segments and by determining, at        each segment of the multiple segments, an additional phase θ for        a state among 16 states of value combination of the four        baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) in the        constant envelope multiplexed signal, based on the determined        power ratio of the four baseband spreading signals s₁(t), s₂(t),        s₃(t), s₄(t);    -   obtaining, according to a segment of the subcarrier period of        the baseband spreading signal and to a state of the value        combination of the four baseband spreading signals s₁(t), s₂(t),        s₃(t) and s₄(t) corresponding to the current time, an additional        phase θ of a segment of the current time by looking up the        additional phase lookup table;    -   generating an in-phase baseband component I(t) and a        quadrature-phase baseband component Q(t) of the constant        envelope multiplexed signal, and generating the constant        envelope multiplexed signal S_(RF)(t) based on the obtained        additional phase θ, where

S _(RF)(t)=I(t)cos(2πf _(p) t)−Q(t)sin(2πf _(p) t),

I(t)=A cos(θ),

Q(t)=A sin(θ),

f _(p)=(f ₁ +f ₂)/2,

T _(s)=1/f _(s),

f _(s)=(f ₁ −f ₂)/2,

-   -   where A is the amplitude of the constant envelope multiplexed        signal S_(RF)(t).

According to a further aspect of the present application, a device forgenerating a dual-frequency constant envelope multiplexed signal withfour spreading signals is disclosed, in which the four basebandspreading signals s₁(t), s₂(t), s₃(t), s₄(t) are modulated to afrequency f₁ and a frequency f₂ respectively, so as to generate theconstant envelope multiplexed signal on a radio carrier frequencyf_(p)=(f₁+f₂)/2, where the signals s₁(t) and s₂(t) are modulated on thefrequency f₁ with carrier phases orthogonal to each other, the signalss₃(t) and s₄(t) are modulated on the frequency f₂ with carrier phasesorthogonal to each other, f₁>f₂, wherein the device further comprises:

-   -   an additional phase lookup table storing unit for storing the        additional phase lookup table, wherein the table includes        additional phases of an in-phase baseband component I(t) and a        quadrature-phase baseband component Q(t) of the constant        envelope multiplexed signal, and the table is configured by        dividing a subcarrier period T_(s) of the baseband spreading        signal into multiple segments and by determining, at each        segment of the multiple segments, an additional phase θ for a        state among 16 states of value combination of the four baseband        spreading signals s₁(t), s₂(t), s₃(t), s₄(t) in the constant        envelope multiplexed signal, based on the determined power ratio        of the four baseband spreading signals s₁(t), s₂(t), s₃(t),        s₄(t);    -   an lookup unit for obtaining, by looking up the additional phase        lookup table according to a segment of the subcarrier period of        the baseband spreading signal and to a state of the value        combination of the four baseband spreading signals s₁(t), s₂(t),        s₃(t) and s₄(t) corresponding to the current time, an additional        phase θ of a segment of the current time;    -   a generating unit for generating an in-phase baseband component        I(t) and a quadrature-phase baseband component Q(t) of the        constant envelope multiplexed signal, and generating the        constant envelope multiplexed signal S_(RF)(t) based on the        obtained additional phase θ, where

S _(RF)(t)=I(t)cos(2πf _(p) t)−Q(t)sin(2πf _(p) t),

I(t)=A cos(θ),

Q(t)=A sin(θ),

f _(p)=(f ₁ +f ₂)/2,

T _(s)=1/f _(s),

f _(s)=(f ₁ −f ₂)/2,

-   -   where A is the amplitude of the constant envelope multiplexed        signal S_(RF)(t).

According to a further aspect of the present application, a constantenvelope multiplexed signal is disclosed, which is generated by theaforementioned method or device for generating the dual-frequencyconstant envelope multiplexed signal with four spreading signals.

According to a further aspect of the present application, an apparatusis disclosed, which comprises means adapted to process a constantenvelope multiplexed signal generated by the aforementioned method ordevice for generating the dual-frequency constant envelope multiplexedsignal with four spreading signals.

According to a further aspect of the present application, a constantenvelope multiplexed signal receiving device is disclosed, whichreceives the constant envelope multiplexed signal generated by theaforementioned method or device for generating the dual-frequencyconstant envelope multiplexed signal with four spreading signals.

According to a further aspect of the present application, a signalreceiving device is disclosed, which receives the aforementionedconstant envelope multiplexed signal, or the constant envelopemultiplexed signal generated by the aforementioned method or device forgenerating the dual-frequency constant envelope multiplexed signal withfour spreading signals, which comprises:

-   -   a receiving unit for receiving the constant envelope multiplexed        signal;    -   a demodulation unit for demodulating a signal component        modulated on the frequency f₁ of the received constant envelope        multiplexed signal, and for demodulating a signal component        modulated on the frequency f₂ of the received constant envelope        multiplexed signal; and    -   a processing unit for obtaining baseband spreading signals s₁(t)        and s₂(t) based on the demodulated signal component which is        modulated on the frequency f₁, and for obtaining baseband        spreading signals s₃(t) and s₄(t) based on the demodulated        signal component which is modulated on the frequency f₂.

According to a further aspect of the present application, a signalreceiving device is disclosed, which receives the aforementionedconstant envelope multiplexed signal, or the constant envelopemultiplexed signal generated by the aforementioned method or device forgenerating the dual-frequency constant envelope multiplexed signal withfour spreading signals, wherein the additional phase lookup table isstored in the signal receiving device and the signal receiving devicecomprises:

-   -   a receiving unit for receiving the constant envelope multiplexed        signal;    -   a demodulation unit for demodulating the received constant        envelope multiplexed signal with a central frequency of        f_(p)=(f₁+f₂)/2 so as to obtain the demodulated baseband signal;    -   an additional phase looking up unit for obtaining, based on the        additional phase lookup table, an additional phase θ        corresponding to each state among states of value combination of        the four baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t);    -   a local replica generating unit for generating, based on the        obtained additional phase θ, a local replica Ĩ_(i)(t) of an        in-phase baseband signal and a local replica {tilde over        (Q)}_(i)(t) of a quadrature-phase baseband signal corresponding        to each state; and    -   a calculating unit for calculating a correlation between the        generated Ĩ_(i)(t) and {tilde over (Q)}_(i)(t) corresponding to        each state with the demodulated baseband signal, to determine        the baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) of the        demodulated baseband signal, so as to achieve the acquisition        and tracking of the constant envelope multiplexed signal.

According to a further aspect of the present application, a signalreceiving device is disclosed, which receives the aforementionedconstant envelope multiplexed signal, or the constant envelopemultiplexed signal generated by the aforementioned method or device forgenerating the dual-frequency constant envelope multiplexed signal withfour spreading signals, wherein the additional phase lookup table isstored in the signal receiving device and the signal receiving devicecomprises:

-   -   a receiving unit for receiving, filtering and amplifying the        constant envelope multiplexed signal, wherein a central        frequency of the filtering and amplifying is set at (f₁+f₂)/2;    -   a demodulation unit for converting a carrier frequency of the        signal component to be processed to a corresponding intermediate        frequency, converting the signal component from analog to        digital by sampling and quantizing the signal, and obtaining a        receiver in-phase baseband signal SI(t) and a receiver        quadrature-phase baseband signal SQ(t) by multiplying the        converted digital intermediate frequency signal by an in-phase        carrier and a quadrature-phase carrier respectively;    -   an additional phase looking up unit for generating a spreading        sequence of four baseband spreading signals with spreading chip        waveform assignment, and generating, based on all the possible        value combinations of the binary baseband local signal replica        of the four baseband spreading signals, an in-phase baseband        signal local replica Ĩ_(i)(t) and a quadrature-phase baseband        signal local replica {tilde over (Q)}_(i)(t) corresponding to        each combination in the additional phase looking up unit, at        each epoch, wherein the number of value combinations is denoted        as g, g=2^(N), where there are N data channels, and for a        special case S_(i)={{tilde over (s)}₁, {tilde over (s)}₂, {tilde        over (s)}₃, {tilde over (s)}₄} among the g value combinations,        the generating rule of Ĩ_(i)(t) and {tilde over (Q)}_(i)(t) is        same as the transmitting device, and for obtaining the        additional phase θ_(i) of the current time by looking up the        additional phase lookup table;    -   a local replica generating unit for generating the in-phase        baseband signal local replica Ĩ_(i)(t) and the quadrature-phase        baseband signal local replica {tilde over (Q)}_(i)(t), where

Ĩ _(i)(t)=cos(θ_(i))

{tilde over (Q)} _(i)(t)=sin(θ_(i)); and

-   -   a calculating unit for obtaining the i-th (i=1, 2, . . . , g)        group of a first in-phase correlation value corr1I_(i) and a        first quadrature-phase correlation value corr1Q_(i) by        multiplying the i-th (i=1, 2, . . . , g) group of the in-phase        baseband signal local replica Ĩ_(i)(t) with the in-phase        baseband signal SI(t) and the quadrature-phase baseband signal        SQ(t) and sending the multiplying results into an integration        and dumping filter for coherent integration with duration of TI,        and for obtaining the i-th (i=1, 2, . . . , g) group of the        second in-phase correlation value corr2I_(i) and the        quadrature-phase correlation value corr2Q_(i) by multiplying        each group of the quadrature-phase baseband signal local replica        {tilde over (Q)}_(i)(t) with the in-phase baseband signal SI(t)        and the quadrature-phase baseband signal SQ(t) and sending the        multiplying results into the integration and dumping filter for        the coherent integration with duration of TI;    -   for obtaining the i-th (i=1, 2, . . . , g) group of in-phase        combination correlation value I′_(i) and the quadrature-phase        combination correlation value Q′_(i) by combining the first        in-phase correlation value corr1I_(i) and the first        quadrature-phase correlation value corr1Q_(i) of the i-th group        with the second in-phase correlation value corr2I_(i) and the        second quadrature-phase correlation value corr2Q_(i) of the i-th        group as:

$\left\{ {\begin{matrix}{I_{i}^{\prime} = {{{corr}\; 2\; I_{i}} + {{corr}\; 1\; Q_{i}}}} \\{Q_{i}^{\prime} = {{{corr}\; 1\; I_{i}} - {{corr}\; 2\; Q_{i}}}}\end{matrix};} \right.$

-   -    and    -   for selecting an optimal in-phase combination correlation value        I′ and an optimal quadrature-phase combination correlation value        Q′ to be a group of in-phase combination correlation value        I_(i)′ and quadrature-phase combination correlation value        Q_(i)′, the value √{square root over (I′_(i) ²+Q′_(i) ²)} of        which is the maximum among all the groups, so as to determine        the baseband spreading signal s₁(t), s₂(t), s₃(t), s₄(t), and to        process I′ and Q′ through traditional acquisition method and        tracking loop.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flowchart of a method for generating adual-frequency constant envelope multiplexed signal with four spreadingsignals according to an embodiment of the application.

FIG. 2 illustrates a schematic diagram of values of Î(t) and {circumflexover (Q)}(t) in a subcarrier period of a baseband spreading signalaccording to an embodiment of the application.

FIG. 3 illustrates a constellation of multiplexed signal S_(RF)(t) whenthe power ratio of the four baseband spreading signals s₁(t), s₂(t),s₃(t), s₄(t) is 1:3:1:3 according to an embodiment of the application.

FIG. 4 illustrates a block diagram of the generating device of thedual-frequency constant envelope multiplexed signal with four spreadingsignals according to an embodiment of the application.

FIG. 5 illustrates an example of generating the constant envelopemultiplexed signal according to an embodiment of the application.

FIG. 6 illustrates a power spectral density (PSD) of the multiplexedsignal according to an embodiment of the application.

FIG. 7 illustrates a receiving device of the dual-frequency constantenvelope multiplexed signal with four spreading signals according to anembodiment of the application.

FIG. 8 illustrates a schematic diagram of the receiving device of thedual-frequency constant envelope multiplexed signal with four spreadingsignals according to an embodiment of the application.

FIG. 9 illustrates a receiving device of the dual-frequency constantenvelope multiplexed signal with four spreading signals, according toanother embodiment of the application.

DETAILED DESCRIPTION

Hereinafter, with reference to the appended drawings, a detaileddescription of the generating method, generating device, receivingmethod and receiving device of the dual-frequency constant envelopemultiplexed signal with four spreading signals will be provided. Forsimplicity, in the description of the embodiments of the presentapplication, the same or similar reference numeral is used for the sameor similar device.

FIG. 1 illustrates a method for generating a dual-frequency constantenvelope multiplexed signal with four spreading signals according to anembodiment of the present application. According to this method, thefour baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) are modulatedto a frequency f₁ and a frequency f₂ respectively, so as to generate theconstant envelope multiplexed signal on a radio carrier frequencyf_(p)=(f₁+f₂)/2, where the signals s₁(t) and s₂(t) are modulated on thefrequency f₁ with carrier phases orthogonal to each other, the signalss₃(t) and s₄(t) are modulated on the frequency f₂ with carrier phasesorthogonal to each other, f₁>f₂, and the generated dual-frequency signalwith four spreading signals is a constant envelope multiplexed signal.

Particularly, as shown in FIG. 1, in Step 110, the power ratio allocatedto the four baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) in theconstant envelope multiplexed signal is determined. The power ratioallocated to the four baseband spreading signals s₁(t), s₂(t), s₃(t),s₄(t) is denoted as c₁:c₂:c₃:c₄ which can be set as any ratio dependingon the applicational requirement. For example, the power ratio can be,but is not limited to be, set as 1:2:1:2, 1:3:1:3 or 1:5:1:5, etc.

In Step 120, an additional phase lookup table is stored. The tableincludes an additional phase of an in-phase baseband component I(t) anda quadrature-phase baseband component Q(t) of the constant envelopemultiplexed signal.

In an embodiment of the present application, the additional phase lookuptable may be configured as follows.

The table may be configured by dividing a subcarrier period T_(s) of thebaseband spreading signal into multiple segments and by determining, ateach segment of the multiple segments, an additional phase θ for a stateamong 16 states of value combination of the four baseband spreadingsignals s₁(t), s₂(t), S₃(t), s₄(t) in the constant envelope multiplexedsignal, based on the determined power ratio c₁:c₂:c₃:c₄ of the fourbaseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t). According to anembodiment of the present application, the additional phase lookup tablemay be preset and stored in a navigation signal transmitter or a signalgenerating device. Therefore, when an additional phase is to bedetermined, it is only needed to look up the additional phase look-uptable, which reduces the calculating complexity of the navigation signaltransmitter or the signal generating device.

In Step 130, by searching the additional phase lookup table according toa segment of the subcarrier period of the baseband spreading signal andto a state of the value combination of the four baseband spreadingsignals s₁(t), s₂(t), s₃(t) and s₄(t) corresponding to the current time,an additional phase θ of a segment of the current time may be obtained.As can be understood, the current time belongs to a certain subcarrierperiod of the baseband spreading signal, which is tε[nT_(s),(n+1)T_(s)). Since the subcarrier period T_(s) is divided into multiplesegments, the current time t corresponds to a certain segment amongthose segments. Moreover, for a current time, the values of the fourbaseband spreading signal s₁(t), s₂(t), s₃(t), s₄(t) correspond to oneof the 16 value combinations. Therefore, it is possible to look up thestored additional phase lookup table so as to obtain the additionalphase of the current segment, based on a certain segment of thesubcarrier period of the baseband spreading signal to which the currenttime corresponds, and a certain one of the 16 value combinations towhich the current value of the four baseband spreading signals s₁(t),s₂(t), s₃(t), s₄(t) corresponds.

In Step 140, based on the obtained additional phase θ, an in-phasebaseband component I(t) and a quadrature-phase baseband component Q(t)of the constant envelope multiplexed signal are generated, and themultiplexed signal S_(RF)(t) with constant envelope is generated, where

S _(RF)(t)=I(t)cos(2πf _(p) t)−Q(t)sin(2πf _(p) t),

I(t)=A cos(θ),

Q(t)=A sin(θ),

f _(p)=(f ₁ +f ₂)/2,

T _(s)=1/f _(s),

f _(s)=(f ₁ −f ₂)/2,

-   -   where A is the amplitude of the constant envelope multiplexed        signal S_(RF)(t). As can be seen, for every current time, or        every segment to which the current time corresponds, it is        possible to look up the additional phase θ so as to generate the        constant envelope multiplexed signal S_(RF)(t), where the        amplitude of the multiplexed signal S_(RF)(t) is a constant A.

Through the method of the present application, the four basebandspreading signal s₁(t), s₂(t), s₃(t), s₄(t) may be modulated on thefrequency f_(p), where the s₁(t) and s₂(t) are modulated on thefrequency f₁ with carrier phases orthogonal to each other, and s₃(t) ands₄(t) are modulated on the frequency f₂ with carrier phases orthogonalto each other. The multiplexed signal modulated on the radio carrierfrequency f_(p), is a constant envelope multiplexed signal.

According to an embodiment of the present application, the additionalphase lookup table may be configured as follows.

As mentioned, according to the method of the present application, fourbaseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) are modulated onthe frequency f₁ and f₂ respectively, so as to generate a constantenvelope multiplexed signal S_(RF)(t) on a radio carrier frequencyf_(p)=(f₁+f₂)/2. For a signal on a carrier frequency f_(p), it ispossible to express the signal through two orthogonal componentsmodulated to the frequency f_(p), which is

S _(RF)(t)=I(t)cos(2πf _(p) t)−Q(t)sin(2πf _(p) t),

-   -   where I(t) is an in-phase baseband component of the constant        envelope multiplexed signal, and Q(t) is a quadrature-phase        baseband component of the constant envelope multiplexed signal.

According to the present application, in the additional phase lookuptable, the additional phase θ of the in-phase baseband component I(t)and quadrature-phase baseband component Q(t) of the constant envelopemultiplexed signal is stored. The additional phase refers to the phase θthat is used to deform the multiplexed signal S_(RF)(t) in the followingexpression:

S _(RF)(t)=I(t)+jQ(t)=Aexp(jθ)

-   -   where A=√{square root over (I²+Q²)} expresses the amplitude of        S_(RF)(t), and the phase θ expresses the additional phase of the        in-phase baseband component I(t) and quadrature-phase baseband        component Q(t) of the multiplexed signal S_(RF)(t).

According to an embodiment of the present application, a preset in-phasebaseband component Î(t) and a preset quadrature-phase baseband component{circumflex over (Q)}(t) can be obtained by the following expressions:

{circumflex over (I)}(t)=Z(t)×sgn[sin(2πf _(s) t+φ(t))],

{circumflex over (Q)}(t)=Z′(t)×sgn[sin(2πf _(s) t+φ′(t))],

-   -   wherein sgn stands for the sign function

${{sgn}(x)} = \left\{ {\begin{matrix}{{+ 1},} & {x \geq 0} \\{{- 1},} & {x < 0}\end{matrix}\begin{matrix}{{Z(t)} = {- \sqrt{\left( {{\sqrt{c_{1}}{s_{1}(t)}} + {\sqrt{c_{3}}{s_{3}(t)}}} \right)^{2} + \left( {{\sqrt{c_{2}}{s_{2}(t)}} - {\sqrt{c_{4}}{s_{4}(t)}}} \right)^{2}}}} \\{{\phi (t)} = {{- a}\; \tan \; 2\left( {{{\sqrt{c_{1}}{s_{1}(t)}} + {\sqrt{c_{3}}{s_{3}(t)}}},{{\sqrt{c_{2}}{s_{2}(t)}} - {\sqrt{c_{4}}{s_{4}(t)}}}} \right)}}\end{matrix}\begin{matrix}{{Z^{\prime}(t)} = \sqrt{\left( {{\sqrt{c_{1}}{s_{1}(t)}} - {\sqrt{c_{3}}{s_{3}(t)}}} \right)^{2} + \left( {{\sqrt{c_{2}}{s_{2}(t)}} + {\sqrt{c_{4}}{s_{4}(t)}}} \right)^{2}}} \\{{\phi^{\prime}(t)} = {a\; \tan \; 2\left( {{{\sqrt{c_{2}}{s_{2}(t)}} + {\sqrt{c_{4}}{s_{4}(t)}}},{{\sqrt{c_{1}}{s_{1}(t)}} - {\sqrt{c_{3}}{s_{3}(t)}}}} \right)}}\end{matrix}} \right.$

-   -   wherein c₁, c₂, c₃, c₄ are relative powers of the four baseband        spreading signals s₁(t), s₂(t), s₃(t), s₄(t), that is, the power        ratio allocated to the four baseband spreading signals s₁(t),        s₂(t), s₃(t), s₄(t) is c₁:c₂:c₃:c₄,    -   atan 2 is the four-quadrant arctangent function,

${a\; \tan \; 2\left( {y,x} \right)} = \left\{ {\begin{matrix}{{{arc}\; {\cos\left( \frac{y}{\sqrt{x^{2} + y^{2}}} \right)}},} & {{x \geq 0},{\sqrt{x^{2} + y^{2}} > 0}} \\{{{- {arc}}\; {\cos\left( \frac{y}{\sqrt{x^{2} + y^{2}}} \right)}},} & {x < 0} \\{0,} & {\sqrt{x^{2} + y^{2}} = 0}\end{matrix}.} \right.$

While the preset in-phase baseband component Î(t) and the presetquadrature-phase baseband component {circumflex over (Q)}(t) areobtained, the multiplexed signal S_(RF)(t) can be expressed as

S _(RF)(t)={circumflex over (I)}(t)+j{circumflex over (Q)}(t)=Aexp(jθ).

Therefore, the value of the additional phase θ can be obtained by

θ=atan 2({circumflex over (Q)}(t),{circumflex over (I)}(t))

where atan 2 is the four-quadrant arctangent function.

In addition, it can be seen that A=√{square root over (I²+Q²)}=√{squareroot over (c₁+c₂+c₃+c₄)} is a constant value without changing over time.Therefore, the dual-frequency constant envelope multiplexed signal withfour spreading signals S_(RF)(t) in the present application is aconstant envelope multiplexed signal. The envelope of the multiplexedsignal can be determined by the relative power, or the power ratio ofthe four baseband spreading signals s₁(t), s₂(t), s₃ (t), s₄(t).

It is appreciated that the method of calculating the additional phase isdescriptive but not limited. Any method for calculating the additionalphase will be included in the present application as long as theadditional phase θ obtained through the method is such that themultiplexed signal S_(RF)(t) is of the constant envelop.

According to an embodiment of the present application, the additionalphase θ=atan 2({circumflex over (Q)}(t), Î(t)) and, as mentioned, atan 2is the four-quadrant arctangent function, and thereby the additionalphase θ is determined by values of Î(t) and {circumflex over (Q)}(t).

FIG. 2 illustrates a schematic diagram of values of Î(t) and {circumflexover (Q)}(t) in a subcarrier period of a baseband spreading signalaccording to an embodiment of the present application. As shown, any ofa preset in-phase baseband component Î(t) and a preset quadrature-phasebaseband component {circumflex over (Q)}(t) of the multiplexed signalS_(RF)(t) is of a square waveform, whose starting points are determinedby φ(t) and φ′(t). Since the additional phase θ=atan 2({circumflex over(Q)}(t), Î(t)) and any of the Î(t) and {circumflex over (Q)}(t) is of asquare waveform, the value of the additional phase θ may shift atmoments when the value of Î(t) or {circumflex over (Q)}(t) flips, forexample, at t₁, t₂, t₃ and t₄ as shown in FIG. 2. Since each of thebaseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) is a basebandsignal with the value of +/−1, there is a total of 16 states ofdifferent value combinations for the four baseband spreading signals,such as (1,1,1,1) or (1,−1,−1,1), etc. Î(t) and {circumflex over (Q)}(t)can be calculated corresponding to each state among the total 16 states,and thus phase-shifting points of the additional phase θ can becalculated. All the phase-shifting points of the additional phase θconstitute a set of the starting points and ending points of segments ina subcarrier period of the baseband spreading signal. That is, theadditional phase θ keeps unchanged during a segment of the subcarrierperiod, and will change in the next segment. Considering that thephase-shifting points of the additional phase θ determined by the 16value combinations of Î(t) and {circumflex over (Q)}(t) may beoverlapped, it can be seen, through calculation, that a subcarrierperiod of the baseband spreading signal can be divided into at most 16segments for various power ratios of the four baseband spreadingsignals.

Hereinafter, a power ratio of the four baseband spreading signals s₁(t),s₂(t), s₃(t), s₄(t) as 1:3:1:3 is given as an exemplary description.

According to the above mentioned method, when the power ratio is1:3:1:3, a subcarrier period of the baseband spreading signal needs tobe divided into 12 segments with equal length. That is, for any currenttime tε[nT_(s), (n+1)T_(s)), the subcarrier period [nT_(s), (n+1)T_(s))is further divided into 12 segments with equal length of T_(s)/12.According to a certain segment of the subcarrier period of the basebandspreading signal [nT_(s), (n+1)T_(s)) to which the current time tbelongs, and a certain one of the 16 states to which the current valuecombination of the four baseband spreading signals s₁(t), s₂(t), s₃(t),s₄(t) corresponds, an additional phase θ corresponding to the currenttime can be looked up in the additional phase lookup table, such as inthe Table 1 or Table 2. In the additional phase lookup table, P1, P2,P3, P4, P5, P6, P7, P8, P9, P10, P11, P12 are 12 different phase values,satisfying

${P_{K} = {P_{1} + \frac{k\; \pi}{6}}},$

corresponding to 12 phase points in a 12-PSK constellation.

FIG. 3 illustrates a Fresnel constellation of multiplexed signalS_(RF)(t) when the power ratio of the four baseband spreading signalss₁(t), s₂(t), s₃(t), s₄(t) is 1:3:1:3, according to an embodiment of thepresent application. According to the embodiment as shown in the FIG. 3,

${P_{1} = \frac{\pi}{6}},$

and, as can be seen, the multiplexed signal is a 12-PSK signal, wherethe constellation points are evenly distributed. When another value isselected for P₁, the constellation may be obtained by rotating the FIG.3 by a certain phase, while the relationship among different phaseskeeps unchanged.

That is, since the rotation of the 12-PSK constellation as a whole willnot influence the receiving side, P₁ can be set as any phase in [0,2π].It is easy to understand that, values of the additional phases in theTable.1 and Table.2 change when different values are set for P₁, whilethe relationship among different phases keeps satisfying

${P_{K} = {P_{1} + \frac{k\; \pi}{6}}},$

and the signal generating rule with respect to the time and signal valuecombination also satisfies the Table 1 or Table 2.

TABLE 1 VS₁ VS₂ VS₃ VS₄ VS₅ VS₆ VS₇ VS₈ VS₉ VS₁₀ VS₁₁ VS₁₂ VS₁₃ VS₁₄VS₁₅ VS₁₆ s₁ (t) 1  1  1  1  1  1  1  1 −1 −1 −1 −1 −1 −1 −1 −1 s₂ (t) 1 1 −1 −1  1  1 −1 −1  1  1 −1 −1  1  1 −1 −1 s₃ (t) 1  1  1  1 −1 −1 −1−1  1  1  1  1 −1 −1 −1 −1 s₄ (t) 1 −1  1 −1  1 −1  1 −1  1 −1  1 −1  1−1  1 −1 t′ = t mod T_(s) t′ ∈ θ [0,T_(s) / 12) P2 P12 P12 P10 P3 P5 P1P9 P3 P7 P11 P9 P4 P6 P6 P8 [T_(s) / 12, 2T_(s) / 12) P2 P6 P12 P10 P3P5 P1 P9 P3 P7 P11 P9 P4 P6 P12 P8 [2T_(s) / 12, 3T_(s) / 12) P2 P6 P12P10 P3 P5 P1 P3 P9 P7 P11 P9 P4 P6 P12 P8 [3T_(s) / 12, 4T_(s) / 12) P8P6 P12 P4 P3 P5 P1 P3 P9 P7 P11 P9 P10 P6 P12 P2 [4T_(s) / 12, 5T_(s) /12) P8 P6 P12 P4 P9 P5 P1 P3 P9 P7 P11 P3 P10 P6 P12 P2 [5T_(s) / 12,6T_(s) / 12) P8 P6 P6 P4 P9 P5 P1 P3 P9 P7 P11 P3 P10 P12 P12 P2 [6T_(s)/ 12, 7T_(s) / 12) P8 P6 P6 P4 P9 P11 P7 P3 P9 P1 P5 P3 P10 P12 P12 P2[7T_(s) / 12,8T_(s) / 12) P8 P12 P6 P4 P9 P11 P7 P3 P9 P1 P5 P3 P10 P12P6 P2 [8T_(s) / 12,9T_(s) / 12) P8 P12 P6 P4 P9 P11 P7 P9 P3 P1 P5 P3P10 P12 P6 P2 [9T_(s) / 12, 10T_(s) / 12) P2 P12 P6 P10 P9 P11 P7 P9 P3P1 P5 P3 P4 P12 P6 P8 [10T_(s) / 12, 11T_(s) / 12) P2 P12 P6 P10 P3 P11P7 P9 P3 P1 P5 P9 P4 P12 P6 P8 [11T_(s) / 12,T_(s)) P2 P12 P12 P10 P3P11 P7 P9 P3 P1 P5 P9 P4 P6 P6 P8

TABLE 2 VS₁ VS₂ VS₃ VS₄ VS₅ VS₆ VS₇ VS₈ VS₉ VS₁₀ VS₁₁ VS₁₂ VS₁₃ VS₁₄VS₁₅ VS₁₆ s₁ (t) 1  1  1  1  1  1  1  1 −1 −1 −1 −1 −1 −1 −1 −1 s₂ (t) 1 1 −1 −1  1  1 −1 −1  1  1 −1 −1  1  1 −1 −1 s₃ (t) 1  1  1  1 −1 −1 −1−1  1  1  1  1 −1 −1 −1 −1 s₄ (t) 1 −1  1 −1  1 −1  1 −1  1 −1  1 −1  1−1  1 −1 t′ = t mod T_(s) t′ θ [0,T_(s) / 12) P1 P12 P12 P11 P3 P4 P2 P9P3 P8 P10 P9 P5 P6 P6 P7 [T_(s) / 12, 2T_(s) / 12) P1 P12 P12 P11 P3 P4P2 P3 P9 P8 P10 P9 P5 P6 P6 P7 [2T_(s) / 12, 3T_(s) / 12) P1 P6 P12 P11P3 P4 P2 P3 P9 P8 P10 P9 P5 P6 P12 P7 [3T_(s) / 12, 4T_(s) / 12) P7 P6P12 P5 P3 P4 P2 P3 P9 P8 P10 P9 P11 P6 P12 P1 [4T_(s) / 12, 5T_(s) / 12)P7 P6 P6 P5 P3 P4 P2 P3 P9 P8 P10 P9 P11 P12 P12 P1 [5T_(s) / 12, 6T_(s)/ 12) P7 P6 P6 P5 P9 P4 P2 P3 P9 P8 P10 P3 P11 P12 P12 P1 [6T_(s) / 12,7T_(s) / 12) P7 P6 P6 P5 P9 P10 P8 P3 P9 P2 P4 P3 P11 P12 P12 P1 [7T_(s)/ 12, 8T_(s) / 12) P7 P6 P6 P5 P9 P10 P8 P9 P3 P2 P4 P3 P11 P12 P12 P1[8T_(s) / 12,9T_(s) / 12) P7 P12 P6 P5 P9 P10 P8 P9 P3 P2 P4 P3 P11 P12P6 P1 [9T_(s) / 12, 10T_(s) / 12) P1 P12 P6 P11 P9 P10 P8 P9 P3 P2 P4 P3P5 P12 P6 P7 [10T_(s) / 12,11T_(s) / 12) P1 P12 P12 P11 P9 P10 P8 P9 P3P2 P4 P3 P5 P6 P6 P7 [11T_(s) / 12,T_(s)) P1 P12 P12 P11 P3 P10 P8 P9 P3P2 P4 P9 P5 P6 P6 P7

-   -   wherein VS_(i), i=1, 2, 3 . . . , 16 stands for the 16 states of        the value combination of the four baseband spreading signals        s₁(t), s₂(t), s₃(t), s₄(t); P_(K), K=1, 2, 3 . . . , 12 stands        for the value of the additional phase θ, with

${P_{K} = {P_{1} + \frac{k\; \pi}{6}}},$

P₁ can be arbitrary phase belonging to [0,2π]; t′=t mod T_(s) shows thatthe additional phase θ is obtained with the modulo of the current time tand the subcarrier period T_(s).

In this way, based on the additional phase θ obtained, the in-phasebaseband component I(t) and quadrature-phase baseband component Q(t) ofthe constant envelope multiplexed signal are generated, and themultiplexed signal with constant envelope S_(RF)(t) is generated, where

S _(RF)(t)=I(t)cos(2πf _(p) t)−Q(t)sin(2πf _(p) t),

I(t)=A cos(θ),

Q(t)=A sin(θ),

f _(p)=(f ₁ +f ₂)/2,

T _(s)=1/f _(s),

f _(s)=(f ₁ −f ₂)/2,

wherein A is the amplitude of the constant envelope multiplexed signalS_(RF)(t).

FIG. 4 illustrates a block diagram of the generating device of thedual-frequency constant envelope multiplexed signal with four spreadingsignals, according to an embodiment of the present application. As shownin FIG. 4, the generating device for the dual-frequency constantenvelope multiplexed signal with four spreading signals comprises anadditional phase lookup table storing unit 410, a lookup unit 420, and agenerating unit 430.

The additional phase lookup table storing unit 410 is configured tostore the mentioned additional phase lookup table, which includesadditional phases of the in-phase baseband component I(t) andquadrature-phase baseband component Q(t) of the multiplexed signal. Theadditional phase lookup table may be preset as follows and stored in theadditional phase lookup table storing unit 410. The additional phaselookup table may be configured by dividing a subcarrier period T_(s) ofthe baseband spreading signal into multiple segments and by determining,at each segment of the multiple segments, an additional phase θ for astate among 16 states of value combination of the four basebandspreading signals s₁(t), s₂(t), s₃(t), s₄(t) in the constant envelopemultiplexed signal, based on the determined power ratio of the fourbaseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t).

The lookup unit 420 is configured to obtain, according to a segment ofthe subcarrier period of the baseband spreading signal and a state ofthe value combination of the four baseband spreading signals s₁(t),s₂(t), s₃(t) and s₄(t) corresponding to the current time, an additionalphase θ of a segment of the current time by looking up the additionalphase lookup table.

The generating unit 430 is configured to generate an in-phase basebandcomponent I(t) and a quadrature-phase baseband component Q(t) of theconstant envelope multiplexed signal, and then generate the constantenvelope multiplexed signal S_(RF)(t) based on the obtained additionalphase θ, where

S _(RF)(t)=I(t)cos(2πf _(p) t)−Q(t)sin(2πf _(p) t),I(t)=A cos(θ),

Q(t)=A sin(θ),

f _(p)=(f ₁ +f ₂)/2,

T _(s)=1/f _(s),

f _(s)=(f ₁ −f ₂)/2,

wherein A is the amplitude of the constant envelope multiplexed signalS_(RF)(t).

FIG. 5 illustrates an example of generating the constant envelopemultiplexed signal, according to an embodiment of the presentapplication. The driving clock of the units is generated through thedivision or multiplication of the reference frequency clock f₀.

The reference frequency clock 20, through the frequency converter 21, isconverted into a data driving clock with a frequency f_(D), which drivesthe message generator 22 to generate four binary navigation messages. Ifa pilot channel is required in some implementations, the navigationmessage of the corresponding channel keeps as being 0 or 1 withoutchanging. The reference frequency clock, through frequency converters23-1, 23-2, 23-3 and 23-4, is converted into the driving clock withfrequency of f_(c1), f_(c2), f_(c3) and f_(c4), respectively, whichdrives spreading modulators 24-1, 24-2, 24-3, and 24-4 to generate fourbinary spreading sequences, respectively, with spreading code rates off_(c1), f_(c2), f_(c3) and f_(c4). Any of the spreading code rates isthe positive integer multiple of f_(D).

The four navigation messages generated by the message generator 22 aretransmitted into the spreading modulators 24-1, 24-2, 24-3 and 24-4respectively, to make module-2 additive combination with the spreadingsequence. The results of the module 2 additive combination are sent intospreading chip waveform generators 26-1, 26-2, 26-3, 26-4 respectively.The spreading chip waveform generator is driven by subcarrier drivingclocks with the frequency of f_(sc1), f_(sc2), f_(sc3) and f_(sc4), intowhich the clock 20 is converted through frequency converters 25-1, 25-2,25-3 and 25-4 respectively. The spreading chip waveform generator makesBCS chip waveform assignment to the spreading sequence modulated withnavigation message, and the outputs are noted as baseband signals s₁(t),s₂(t) s₃(t), s₄(t) respectively. Where f_(sc1)=K₁f_(c1),f_(sc2)=K₂f_(c2), f_(sc3)=K₃f_(c3), f_(sc4)=K₄f_(c4), and K₁, K₂, K₃, K₄are integers greater than or equal to 1.

The clock 20, through the frequency converter 29, is converted to adriving clock with a frequency of 12f_(s), which drives an additionalphase table lookup unit 27 and an I-channel trigonometric functiongenerator 31 and a Q-channel trigonometric function generator 32.

s₁(t), s₂(t), s₃(t), s₄ (t) are sent into the additional phase tablelookup unit 27, which obtains the additional phase offset θ by the tablelooking-up, based on the value combination of s₁(t), s₂(t), s₃(t),s₄(t), corresponding to the current time slot and the modulo of thecurrent time t and the subcarrier period T_(s)=1/f_(s). The lookup tableis in the form of Table 1 or Table 2. In the lookup table, P1, P2, P3,P4, P5, P6, P7, P8, P9, P10, P11, P12 are 12 different phase values,satisfying

${P_{K} = {P_{1} + \frac{k\; \pi}{6}}},$

corresponding to the phase points in a 12-PSK constellation. P₁ may beset as any phase in [0,2π]. As the value of P₁ may be changed, the truevalue of the additional phases in Table 1 or Table 2 may be changed.Hence there are numerous possible values for the lookup table in theapplication, while the relationship among different phases in the tablekeeps satisfying

${P_{K} = {P_{1} + \frac{k\; \pi}{6}}},$

and the signal generating rule with respect to the time and signal valuecombination also satisfies Table 1 or Table 2.

The I-channel trigonometric function generator 31 and the Q-channeltrigonometric function generator 32, based on the output phase θ of theadditional phase table lookup unit 27, generates the components I(t) andQ(t) in accordance with the following rules respectively, where I(t)=Acos (θ), Q(t)=A sin (θ), in which A is the amplitude with positive valueand does not change over time.

The reference clock 20, through a frequency converter 36, is convertedto a driving clock with a frequency of f_(p), which drives a firstcarrier generator 37 to generate a carrier with the frequency of L. Thecarrier signal is divided into two branches. The carrier signal of abranch 40 and the output of the I-channel trigonometric functiongenerator 31 are sent into a multiplier 33. The carrier signal of theother branch 41, after passing through π/2 phase shifting circuit 35,turns into a carrier signal with a phase orthogonal to that of thebranch 40. The carrier signal of the other branch 41 and the output ofthe Q-channel trigonometric function generator 32 are sent into amultiplier 34. The outputs of the two multipliers are sent into an adder38 so as to generate the constant envelope multiplexed signal 39according to the application.

FIG. 6 illustrates a power spectral density (PSD) of the multiplexedbaseband signal, with rectangular pulse spreading waveform (i.e. BPSK-Rmodulation) adopted for each signal component,f_(c1)=f_(c2)=f_(c3)=f_(c4)=10.23 MHz, and f_(s)=15.345 MHz, accordingto an embodiment of the present application. In the PSD, the two signalcomponents sharing the same frequency are combined together and it isdifficult to distinguish the power allocation of each other. However, inthe present embodiment, the upper sideband main lobe 51 with the centralfrequency of f₁ is 30.69 MHz away from the lower sideband main lobe 50with the central frequency of f², and the bandwidth between the spectralzero-crossing points of the two lobes 50 and 51 is 20.46 MHz,corresponding to the design specifications that BPSK-R modulation with10.23 MHz code rate is used for each signal components, and the distancebetween the central frequency of the two main lobes is 30.96 MHz.

As shown in the PSD, the two signal components sharing the samefrequency are combined together, and it is difficult to distinguish thepower allocation of each component. However, by using the receivingmethod 1 to receive the signal, it can be verified the combination ofthe four signals with the power ratio of 1:3:1:3 is achieved through themultiplexed signal.

According to the application, the four baseband spreading signals aremultiplexed into a constant envelope multiplexed signal. The spreadingcodes of the four baseband spreading signals are of good orthogonality.In terms of the receiving and processing of the multiplexed signal, notonly each signal component of the multiplexed signal independently butalso the multiplexed signal as a whole can be received and processed inthe receiver.

Embodiments of the present application described above are mainlyinvolved with the transmission side, that is, with methods and devicesfor generating the dual-frequency constant envelope multiplexed signalwith four spreading signals. In addition, embodiments of the presentapplication also relate to signals generated through such methods anddevices for generating constant envelope multiplexed signal generatingas those described above.

Moreover, as can be appreciated by those skilled in the art, conversesystem, method, apparatus and receiver can be applied to receive andprocess the signals generated in the embodiments of the presentapplication. Therefore, the embodiments of the present application alsorelate to systems, methods, and devices used for processing, forexample, constant envelope multiplexed signals as described above.

According to an embodiment of the present application, a receivingdevice is provided for receiving the dual-frequency constant envelopemultiplexed signal with four spreading signals generated by theaforementioned generating methods or the generating devices. In thepresent embodiment, the signal components modulated on the frequency f₁and the frequency f₂ can be processed respectively.

In an embodiment of the present application, a receiving device isprovided for the dual-frequency constant envelope multiplexed signalwith four spreading signals. As shown in the FIG. 7, a signal receivingdevice 500 includes a receiving unit 510, a demodulation unit 520, and aprocessing unit 530.

The receiving unit 510 is configured to receive the constant envelopemultiplexed signal. The demodulation unit 520 is configured todemodulate a signal component modulated on the frequency f₁ of thereceived constant envelope multiplexed signal, and to demodulate asignal component modulated on the frequency f₂ of the received constantenvelope multiplexed signal. The processing unit 530 is configured toobtain the baseband spreading signals S₁ and S₂ according to thedemodulated signal component which is modulated on the frequency f₁, andto obtain the baseband spreading signals S₃ and S₄ according to thedemodulated signal component which is modulated on the frequency f₂.

FIG. 8 illustrates the schematic diagram of a particular implementationof the receiving device for the dual-frequency constant envelopemultiplexed signal with four spreading signals, according to anembodiment of the present application. According to the embodiment, thereceiving unit 510 may include an antenna 61; the demodulation unit 520may include a filtering amplification unit 62, a downconverter 63, andan Analog to Digital Converter (ADC) 64; and the processing unit 530 mayinclude a digital signal processing unit 65.

Referring to FIG. 8, when signal components are received separately, theconstant envelope multiplexed signal 60 is received from antenna 61.After received by the antenna 61, the received constant envelopemultiplexed signal 60 is sent into the filtering amplification unit 62,where the constant envelope multiplexed signal 60 is filtered, in orderto resist the strong interference signals and out-of-band noises, andthen the constant envelope multiplexed signal 60 is amplified. Whenprocessing the upper sideband signal component s₁(t) or s₂(t), thecentral frequency of the filtering unit is set near f₁, with bandwidthgreater than or equal to the bandwidth of the signal component s₁(t) ors₂(t) to be received, in order to ensure that enough power of the signalcomponent s₁(t) or s₂(t) passes the filtering unit; similarly, whenprocessing the upper sideband signal component s₃(t) or s₄(t), thecentral frequency of filter is set near f₂, with bandwidth greater thanor equal to the bandwidth of the signal component s₃(t) or s₄(t) to bereceived, in order to ensure that enough power of the signal components₃(t) or s₄(t) passes the filtering unit.

The filtered and amplified signal from the filtering amplification unit62 is sent into the downconverter 63, in order to translate the carrierfrequency of the signal component to a corresponding IntermediateFrequency (IF); then the signal is sent into the ADC 64 for the samplingand quantization of the signal, and a digital IF signal is obtained.

The digital IF signal from the ADC 64 is sent into the digital signalprocessing unit 65. This unit can be implemented by FPGA, ASIC,universal computing unit or the combination of the aforementioneddevices, so as to achieve the corresponding acquisition, tracking,demodulation to the baseband signal component to be processed.

Moreover, according to an embodiment of the present application, areceiving method is provided for receiving the dual-frequency constantenvelope multiplexed signal with four spreading signals generated by theaforementioned constant envelope multiplexed signal generating method orgenerating device. The signal receiving method comprises: receiving theconstant envelope multiplexed signal; demodulating the signal componentmodulated on the frequency f₁ of the received constant envelopemultiplexed signal, and demodulating the signal component modulated onthe frequency f₂; obtaining the baseband spreading signal S_(i) and S₂based on the demodulated signal component which is modulated on thefrequency f₁, and obtaining the baseband spreading signal S₃ and S₄based on the demodulated signal component which is modulated on thefrequency f₂.

According to an embodiment of the present application, a receivingdevice is provided for receiving the dual-frequency constant envelopemultiplexed signal with four spreading signals generated by theaforementioned constant envelope multiplexed signal generating method orgenerating device. In this embodiment, the received constant envelopemultiplexed signal with a central frequency of (f₁+f₂)/2 can beprocessed as a whole.

FIG. 9 illustrates a receiving device for the dual-frequency constantenvelope multiplexed signal with four spreading signals, according toanother embodiment of the present application. As shown in the FIG. 9,the receiving device comprises a receiving unit 610, a demodulation unit620, an additional phase looking up unit 630, a local replica generatingunit 640 and a calculating unit 650.

The receiving unit 610 is configured to receive the constant envelopemultiplexed signal. The demodulation unit 620 is configured todemodulate the received constant envelope multiplexed signal with acentral frequency of f_(p)=(f₁+f₂)/2 so as to obtain the demodulatedbaseband signal. The additional phase looking up unit 630 is configuredto obtain an additional phase θ corresponding to each state among statesof value combination of the four baseband spreading signals s₁(t),s₂(t), s₃(t), s₄(t) based on the additional phase lookup table. Thelocal replica generating unit 640 is configured to generate a localreplica Ĩ_(i)(t) of an in-phase baseband signal and a local replica{tilde over (Q)}_(i)(t) of a quadrature-phase baseband signalcorresponding to each state based on the obtained additional phase θ.The calculating unit 650 is configured to calculate a correlationbetween the generated Ĩ_(i)(t) and {tilde over (Q)}_(i)(t) correspondingto each state with the demodulated baseband signal, so as to determinethe baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) of thedemodulated baseband signal.

As can be understood, since the value of the baseband signal is +/−1,the combination of four baseband signal values [S_(i), S₂, S₃, S₄] mayhave up to 16 combination states. The calculating unit 650 may,corresponding to each of the 16 combination states, calculate acorrelation between the in-phase baseband component local replica andthe quadrature-phase baseband component local replica with the in-phasebaseband component and the quadrature-phase baseband component obtainedfrom the demodulation unit 640, so as to determine values of thereceived first baseband signal S₁, the second baseband signal S₂, thethird baseband signal S₃, and the forth baseband signal S₄. Besides, theacquisition and tracking of the constant envelope multiplexed signal canbe achieved.

Referring to FIG. 9 again, a particular implementation of the receivingdevice for the dual-frequency constant envelope multiplexed signal withfour spreading signals is illustrated, according to another embodimentof the present application. When the multiplexed signal is received andprocessed as a whole, the constant envelope multiplexed signal isreceived by the receiving unit 610 of the receiver. The receivedconstant envelope multiplexed signal from the antenna of the receivingunit 610 is sent into the filtering amplification unit of the receivingunit 610, for filtering the constant envelope multiplexed signal toresist the strong interference signals and out-of-band noises, and foramplifying the constant envelope multiplexed signal. The centralfrequency of filtering unit is set near (f₁+f₂)/2 with a bandwidthgreater than or equal to 2f_(s), to ensure that enough power of thewhole multiplexed signal passes the filtering unit. If the filteringunit can designed appropriately, it is suggested to ensure that thefirst main lobe power of every signal component passes the filteringunit.

The filtered and amplified signal from the filtering amplification unitof the receiving unit 610 is sent into the downconverter of thedemodulation 620, to convert the carrier frequency of the signalcomponent to an Intermediate Frequency (IF); then the signal is sentinto the ADC of the demodulation unit 620 for the sampling andquantization of the signal, to obtain a digital IF signal.

The digital IF signal from the ADC of the demodulation unit 620 is sentinto the digital signal processing unit of the demodulation unit 620.This unit can be implemented by FPGA, ASIC, universal computing unit orthe combination of the aforementioned devices. The digital IF signal ismultiplied by the in-phase carrier and quadrature-phase carriergenerated by the receiver, in order to remove the IF and Doppler of thedigital signal, so as to obtain the receiver in-phase baseband signalSI(t) and the receiver quadrature-phase baseband signal SQ(t).

The digital signal processing unit of the demodulation unit 620 isconfigured to generate spreading sequences of four signals withspreading chip waveform assignment. According to all the possible valuecombinations of the binary baseband local signal replica of the foursignals, the in-phase baseband waveform local replica Ĩ_(i)(t) and thequadrature-phase baseband waveform local replica {tilde over (Q)}_(i)(t)are generated by the digital signal processing unit of the demodulationunit 620 corresponding to each combination, at each epoch. The totalnumber of value combinations is noted as g. It can be calculated that ifN signals relate to data channels, there is g=2^(N). For a specificinstance among the g value combinations of S_(i)={{tilde over (s)}₁,{tilde over (s)}₂, {tilde over (s)}₃, {tilde over (s)}₄}, the generatingrule of Ĩ_(i)(t) and {tilde over (Q)}_(i)(t) is same as the transmitter.The phase additional phase looking up unit 630 obtains the additionalphase θ_(i), corresponding to the current time by searching the phaselookup table.

The local replica generating unit 640 generates the in-phase basebandsignal local replica Ĩ_(i)(t) and the quadrature-phase baseband signallocal replica {tilde over (Q)}_(i)(t), where

Ĩ _(i)(t)=cos(θ_(i))

{tilde over (Q)} _(i)(t)=sin(θ_(i)).

The calculating unit 650 obtains the i-th (i=1, 2, . . . , g) group of afirst in-phase correlation value corr1I_(i) and a first quadrature-phasecorrelation value corr1Q_(i) by multiplying the i-th (i=1, 2, . . . , g)group of the in-phase baseband signal local replica Ĩ_(i)(t) with thein-phase baseband signal SI(t) and the quadrature-phase baseband signalSQ(t) and sending the multiplying results into an integration anddumping filter for coherent integration with duration of TI, and obtainsthe i-th (i=1, 2, . . . , g) group of the second in-phase correlationvalue corr2I_(i) and the quadrature-phase correlation value corr2Q_(i)by multiplying each group of the quadrature-phase baseband signal localreplica {tilde over (Q)}_(i)(t) with the in-phase baseband signal SI(t)and the quadrature-phase baseband signal SQ(t) and sending themultiplying results into the integration and dumping filter for thecoherent integration with duration of TI.

The calculating unit 650 obtains the i-th (i=1, 2, . . . , g) group ofin-phase combination correlation value I′_(i) and the quadrature-phasecombination correlation value Q′_(i) by combining the first in-phasecorrelation value corr1I_(i) and the first quadrature-phase correlationvalue corr1Q_(i) of the i-th group with the second in-phase correlationvalue corr2I_(i) and the second quadrature-phase correlation valuecorr2Q_(i) of the i-th group as:

$\left\{ {\begin{matrix}{I_{i}^{\prime} = {{{corr}\; 2I_{i}} + {{corr}\; 1\; Q_{i}}}} \\{Q_{i}^{\prime} = {{{corr}\; 1I_{i}} - {{corr}\; 2Q_{i}}}}\end{matrix},} \right.$

The calculating unit 650 selects an optimal in-phase combinationcorrelation value I′ and an optimal quadrature-phase combinationcorrelation value Q_(i)′ to be a group of in-phase combinationcorrelation value I_(i)′ and quadrature-phase combination correlationvalue Q′, the value √{square root over (I′_(i) ²+Q′_(i) ²)} of which isthe maximum among all the groups, so as to determine the basebandspreading signal s₁(t), s₂(t), s₃(t), s₄(t), and to process with I′ andQ′ through traditional acquisition method and tracking loop.

Embodiments of the present application may be implemented by hardware,software or the combination thereof. An aspect of the presentapplication provides a program including executable instructions toimplement the constant envelope multiplexed signal generating method,generating device, the constant envelope multiplexed signal receivingmethod, receiving device according to embodiments of the presentapplication. In addition, the program can be stored in storage of anyform, such as optical or magnetic readable media, chip, ROM, PROM, orany form of volatile or non-volatile memory device. According to anexample of the embodiment of the present application, a machine-readablestorage is provided for storing the program.

While various embodiments of the present application have been describedabove referring to the drawings, it should be understood that they havebeen presented by way of example only, and not limitation. It will beapparent to those skilled in the art that various changes in form anddetail can be made therein without departing from the spirit and scopeof the invention.

What is claimed is:
 1. A method for generating a dual-frequency constantenvelope multiplexed signal with four spreading signals, in which thefour baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) are modulatedto a frequency f₁ and a frequency f₂ respectively, so as to generate theconstant envelope multiplexed signal on a radio carrier frequencyf_(p)=(f₁+f₂)/2, where the signals s₁(t) and s₂(t) are modulated on thefrequency f₁ with carrier phases orthogonal to each other, and thesignals s₃(t) and s₄(t) are modulated on the frequency f₂ with carrierphases orthogonal to each other, f₁>f₂, wherein the method furthercomprises: determining a power ratio allocated to the four basebandspreading signals s₁(t), s₂(t), s₃(t), s₄(t) in the constant envelopemultiplexed signal; storing an additional phase lookup table, whereinthe table includes additional phases of an in-phase baseband componentI(t) and a quadrature-phase baseband component Q(t) of the constantenvelope multiplexed signal, and the table is configured by dividing asubcarrier period T_(s) of the baseband spreading signal into multiplesegments and by determining, at each segment of the multiple segments,an additional phase θ for a state among 16 states of value combinationof the four baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) in theconstant envelope multiplexed signal, based on the determined powerratio of the four baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t);obtaining, according to a segment of the subcarrier period of thebaseband spreading signal and to a state of the value combination of thefour baseband spreading signals s₁(t), s₂(t), s₃(t) and s₄(t)corresponding to the current time, an additional phase θ of a segment ofthe current time by looking up the additional phase lookup table;generating an in-phase baseband component I(t) and a quadrature-phasebaseband component Q(t) of the constant envelope multiplexed signal, andgenerating the constant envelope multiplexed signal S_(RF)(t) based onthe obtained additional phase θ, whereS _(RF)(t)=I(t)cos(2πf _(p) t)−Q(t)sin(2πf _(p) t),I(t)=A cos(θ),Q(t)=A sin(θ),f _(p)=(f ₁ +f ₂)/2,T _(s)=1/f _(s),f _(s)=(f ₁ −f ₂)/2, where A is the amplitude of the constant envelopemultiplexed signal S_(RF)(t).
 2. The method as claimed in claim 1,wherein the additional phase lookup table is configured by: obtaining apreset in-phase baseband component Î(t) and a preset quadrature-phasebaseband component {circumflex over (Q)}(t):{circumflex over (I)}(t)=Z(t)×sgn[sin(2πf _(s) t+φ(t))],{circumflex over (Q)}(t)=Z′(t)×sgn[sin(2πf _(s) t+φ′(t))], wherein sgnstands for the sign function ${{sgn}(x)} = \left\{ {\begin{matrix}{{+ 1},} & {x \geq 0} \\{{- 1},} & {x < 0}\end{matrix},\begin{matrix}{{Z(t)} = {- \sqrt{\left( {{\sqrt{c_{1}}{s_{1}(t)}} + {\sqrt{c_{3}}{s_{3}(t)}}} \right)^{2} + \left( {{\sqrt{c_{2}}{s_{2}(t)}} - {\sqrt{c_{4}}{s_{4}(t)}}} \right)^{2}}}} \\{{\phi (t)} = {{- a}\; \tan \; 2\left( {{{\sqrt{c_{1}}{s_{1}(t)}} + {\sqrt{c_{3}}{s_{3}(t)}}},{{\sqrt{c_{2}}{s_{2}(t)}} - {\sqrt{c_{4}}{s_{4}(t)}}}} \right)}}\end{matrix},\begin{matrix}{{Z^{\prime}(t)} = \sqrt{\left( {{\sqrt{c_{1}}{s_{1}(t)}} - {\sqrt{c_{3}}{s_{3}(t)}}} \right)^{2} + \left( {{\sqrt{c_{2}}{s_{2}(t)}} + {\sqrt{c_{4}}{s_{4}(t)}}} \right)^{2}}} \\{{\phi^{\prime}(t)} = {a\; \tan \; 2\left( {{{\sqrt{c_{2}}{s_{2}(t)}} + {\sqrt{c_{4}}{s_{4}(t)}}},{{\sqrt{c_{1}}{s_{1}(t)}} - {\sqrt{c_{3}}{s_{3}(t)}}}} \right)}}\end{matrix},} \right.$ wherein c₁, c₂, c₃, c₄ are relative powers ofthe four baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t)respectively, and the power ratio allocated to the four basebandspreading signals s₁(t), s₂(t), s₃(t), s₄(t) is c₁:c₂:c₃:c₄, atan 2 isthe four-quadrant arctangent function,${a\; \tan \; 2\left( {y,x} \right)} = \left\{ {\begin{matrix}{{{arc}\; {\cos\left( \frac{y}{\sqrt{x^{2} + y^{2}}} \right)}},} & {{x \geq 0},{\sqrt{x^{2} + y^{2}} > 0}} \\{{{- {arc}}\; {\cos\left( \frac{y}{\sqrt{x^{2} + y^{2}}} \right)}},} & {x < 0} \\{0,} & {\sqrt{x^{2} + y^{2}} = 0}\end{matrix};} \right.$  and obtaining the value of the additional phaseθ in the additional phase lookup table as θ=atan 2({circumflex over(Q)}(t), Î(t)).
 3. The method as claimed in claim 2, wherein theprocedure of dividing a subcarrier period T_(s) of the basebandspreading signal into multiple segments based on the determined powerratio of the four baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t)comprises: calculating an additional phase 0=atan 2({circumflex over(Q)}(t), Î(t)) in a subcarrier period T_(s) of the baseband spreadingsignal for each state of value combination of the four basebandspreading signals s₁(t), s₂(t), s₃(t), s₄(t), based on the determinedpower ratio of the four baseband spreading signals s₁(t), s₂(t), s₃(t),S₄; and determining phase-shifting time points of the additional phase θin the subcarrier period T_(s) of the baseband spreading signal, anddividing the subcarrier period T_(s) of the baseband spreading signalinto multiple segments according to the phase-shifting time points. 4.The method as claimed in claim 1, wherein the power ratio of the fourbaseband spreading signals s₁(t), s₂(t), S₃(t), S₄(t) is 1:3:1:3, andthe subcarrier period T_(s) of the baseband spreading signal is dividedinto 12 segments with equal length, and the additional phase lookuptable is in the form of Table 1 or Table 2: TABLE 1 VS₁ VS₂ VS₃ VS₄ VS₅VS₆ VS₇ VS₈ VS₉ VS₁₀ VS₁₁ VS₁₂ VS₁₃ VS₁₄ VS₁₅ VS₁₆ s₁ (t) 1  1  1  1  1 1  1  1 −1 −1 −1 −1 −1 −1 −1 −1 s₂ (t) 1  1 −1 −1  1  1 −1 −1  1  1 −1−1  1  1 −1 −1 s₃ (t) 1  1  1  1 −1 −1 −1 −1  1  1  1  1 −1 −1 −1 −1 s₄(t) 1 −1  1 −1  1 −1  1 −1  1 −1  1 −1  1 −1  1 −1 t′ = t mod T_(s) t′ ∈θ [0,T_(s) / 12) P2 P12 P12 P10 P3 P5 P1 P9 P3 P7 P11 P9 P4 P6 P6 P8[T_(s) / 12, 2T_(s) / 12) P2 P6 P12 P10 P3 P5 P1 P9 P3 P7 P11 P9 P4 P6P12 P8 [2T_(s) / 12, 3T_(s) / 12) P2 P6 P12 P10 P3 P5 P1 P3 P9 P7 P11 P9P4 P6 P12 P8 [3T_(s) / 12, 4T_(s) / 12) P8 P6 P12 P4 P3 P5 P1 P3 P9 P7P11 P9 P10 P6 P12 P2 [4T_(s) / 12, 5T_(s) / 12) P8 P6 P12 P4 P9 P5 P1 P3P9 P7 P11 P3 P10 P6 P12 P2 [5T_(s) / 12, 6T_(s) / 12) P8 P6 P6 P4 P9 P5P1 P3 P9 P7 P11 P3 P10 P12 P12 P2 [6T_(s) / 12, 7T_(s) / 12) P8 P6 P6 P4P9 P11 P7 P3 P9 P1 P5 P3 P10 P12 P12 P2 [7T_(s) / 12, 8T_(s) / 12) P8P12 P6 P4 P9 P11 P7 P3 P9 P1 P5 P3 P10 P12 P6 P2 [8T_(s) / 12, 9T_(s) /12) P8 P12 P6 P4 P9 P11 P7 P9 P3 P1 P5 P3 P10 P12 P6 P2 [9T_(s) /12,10T_(s) / 12) P2 P12 P6 P10 P9 P11 P7 P9 P3 P1 P5 P3 P4 P12 P6 P8[10T_(s) / 12,11T_(s) / 12) P2 P12 P6 P10 P3 P11 P7 P9 P3 P1 P5 P9 P4P12 P6 P8 [11T_(s) / 12,T_(s)) P2 P12 P12 P10 P3 P11 P7 P9 P3 P1 P5 P9P4 P6 P6 P8

TABLE 2 VS₁ VS₂ VS₃ VS₄ VS₅ VS₆ VS₇ VS₈ VS₉ VS₁₀ VS₁₁ VS₁₂ VS₁₃ VS₁₄VS₁₅ VS₁₆ s₁ (t) 1  1  1  1  1  1  1  1 −1 −1 −1 −1 −1 −1 −1 −1 s₂ (t) 1 1 −1 −1  1  1 −1 −1  1  1 −1 −1  1  1 −1 −1 s₃ (t) 1  1  1  1 −1 −1 −1−1  1  1  1  1 −1 −1 −1 −1 s₄ (t) 1 −1  1 −1  1 −1  1 −1  1 −1  1 −1  1−1  1 −1 t′ = t mod T_(s) t′ θ [0,T_(s) / 12) P1 P12 P12 P11 P3 P4 P2 P9P3 P8 P10 P9 P5 P6 P6 P7 [T_(s) / 12, 2T_(s) / 12) P1 P12 P12 P11 P3 P4P2 P3 P9 P8 P10 P9 P5 P6 P6 P7 [2T_(s) / 12, 3T_(s) / 12) P1 P6 P12 P11P3 P4 P2 P3 P9 P8 P10 P9 P5 P6 P12 P7 [3T_(s) / 12, 4T_(s) / 12) P7 P6P12 P5 P3 P4 P2 P3 P9 P8 P10 P9 P11 P6 P12 P1 [4T_(s) / 12, 5T_(s) / 12)P7 P6 P6 P5 P3 P4 P2 P3 P9 P8 P10 P9 P11 P12 P12 P1 [5T_(s) / 12,6T_(s)/ 12) P7 P6 P6 P5 P9 P4 P2 P3 P9 P8 P10 P3 P11 P12 P12 P1 [6T_(s) / 12,7T_(s) / 12) P7 P6 P6 P5 P9 P10 P8 P3 P9 P2 P4 P3 P11 P12 P12 P1 [7T_(s)/ 12, 8T_(s) / 12) P7 P6 P6 P5 P9 P10 P8 P9 P3 P2 P4 P3 P11 P12 P12 P1[8T_(s) / 12,9T_(s) / 12) P7 P12 P6 P5 P9 P10 P8 P9 P3 P2 P4 P3 P11 P12P6 P1 [9T_(s) / 12,10T_(s) / 12) P1 P12 P6 P11 P9 P10 P8 P9 P3 P2 P4 P3P5 P12 P6 P7 [10T_(s) / 12,11T_(s) / 12) P1 P12 P12 P11 P9 P10 P8 P9 P3P2 P4 P3 P5 P6 P6 P7 [11T_(s) / 12,T_(s)) P1 P12 P12 P11 P3 P10 P8 P9 P3P2 P4 P9 P5 P6 P6 P7

wherein VS_(i), i=1, 2, 3 . . . , 16 stands for 16 states of valuecombination of the four baseband spreading signals s₁(t), s₂(t), s₃(t),s₄(t); P_(K), K=1, 2, 3 . . . , 12 stands for value of the additionalphase θ, where ${P_{K} = {P_{1} + \frac{k\; \pi}{6}}},$  and P₁ is anyphase in [0,2π].
 5. A device for generating a dual-frequency constantenvelope multiplexed signal with four spreading signals, in which thefour baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t) are modulatedto a frequency f₁ and a frequency f₂ respectively, so as to generate theconstant envelope multiplexed signal on a radio carrier frequencyf_(p)=(f₁+f₂)/2, where the signals s₁(t) and s₂(t) are modulated on thefrequency f₁ with carrier phases orthogonal to each other, the signalss₃(t) and s₄(t) are modulated on the frequency f₂ with carrier phasesorthogonal to each other, f₁>f₂, wherein the device further comprises:an additional phase lookup table storing unit for storing the additionalphase lookup table, wherein the table includes additional phases of anin-phase baseband component I(t) and a quadrature-phase basebandcomponent Q(t) of the constant envelope multiplexed signal, and thetable is configured by dividing a subcarrier period T_(s) of thebaseband spreading signal into multiple segments and by determining, ateach segment of the multiple segments, an additional phase θ for a stateamong 16 states of value combination of the four baseband spreadingsignals s₁(t), s₂(t), s₃(t), s₄(t) in the constant envelope multiplexedsignal, based on the determined power ratio of the four basebandspreading signals s₁(t), s₂(t), s₃(t), s₄(t); an lookup unit forobtaining, by looking up the additional phase lookup table according toa segment of the subcarrier period of the baseband spreading signal andto a state of the value combination of the four baseband spreadingsignals s₁(t), s₂(t), s₃(t) and s₄(t) corresponding to the current time,an additional phase θ of a segment of the current time; a generatingunit for generating an in-phase baseband component I(t) and aquadrature-phase baseband component Q(t) of the constant envelopemultiplexed signal, and generating the constant envelope multiplexedsignal S_(RF)(t) based on the obtained additional phase θ, whereS _(RF)(t)=I(t)cos(2πf _(p) t)−Q(t)sin(2πf _(p) t),I(t)=A cos(θ),Q(t)=A sin(θ),f _(p)=(f ₁ +f ₂)/2,T _(s)=1/f _(s),f _(s)=(f ₁ −f ₂)/2, where A is the amplitude of the constant envelopemultiplexed signal S_(RF)(t).
 6. The device as claimed in claim 5,wherein the power ratio of the four baseband spreading signals s₁(t),s₂(t), s₃(t), s₄(t) is 1:3:1:3, and the subcarrier period T_(s) of thebaseband spreading signal is divided into 12 segments with equal length,and the additional phase lookup table stored in the additional phaselookup table storing unit is in the form of Table 1 or Table 2: TABLE 1VS₁ VS₂ VS₃ VS₄ VS₅ VS₆ VS₇ VS₈ VS₉ VS₁₀ VS₁₁ VS₁₂ VS₁₃ VS₁₄ VS₁₅ VS₁₆s₁ (t) 1  1  1  1  1  1  1  1 −1 −1 −1 −1 −1 −1 −1 −1 s₂ (t) 1  1 −1 −1 1  1 −1 −1  1  1 −1 −1  1  1 −1 −1 s₃ (t) 1  1  1  1 −1 −1 −1 −1  1  1 1  1 −1 −1 −1 −1 s₄ (t) 1 −1  1 −1  1 −1  1 −1  1 −1  1 −1  1 −1  1 −1t′ = t mod T_(s) t′ ∈ θ [0,T_(s) / 12) P2 P12 P12 P10 P3 P5 P1 P9 P3 P7P11 P9 P4 P6 P6 P8 [T_(s) / 12, 2T_(s) / 12) P2 P6 P12 P10 P3 P5 P1 P9P3 P7 P11 P9 P4 P6 P12 P8 [2T_(s) / 12, 3T_(s) / 12) P2 P6 P12 P10 P3 P5P1 P3 P9 P7 P11 P9 P4 P6 P12 P8 [3T_(s) / 12, 4T_(s) / 12) P8 P6 P12 P4P3 P5 P1 P3 P9 P7 P11 P9 P10 P6 P12 P2 [4T_(s) / 12, 5T_(s) / 12) P8 P6P12 P4 P9 P5 P1 P3 P9 P7 P11 P3 P10 P6 P12 P2 [5T_(s) / 12, 6T_(s) / 12)P8 P6 P6 P4 P9 P5 P1 P3 P9 P7 P11 P3 P10 P12 P12 P2 [6T_(s) / 12, 7T_(s)/ 12) P8 P6 P6 P4 P9 P11 P7 P3 P9 P1 P5 P3 P10 P12 P12 P2 [7T_(s) / 12,8T_(s) / 12) P8 P12 P6 P4 P9 P11 P7 P3 P9 P1 P5 P3 P10 P12 P6 P2 [8T_(s)/ 12, 9T_(s) / 12) P8 P12 P6 P4 P9 P11 P7 P9 P3 P1 P5 P3 P10 P12 P6 P2[9T_(s) / 12,10T_(s) / 12) P2 P12 P6 P10 P9 P11 P7 P9 P3 P1 P5 P3 P4 P12P6 P8 [10T_(s) / 12,11T_(s) / 12) P2 P12 P6 P10 P3 P11 P7 P9 P3 P1 P5 P9P4 P12 P6 P8 [11T_(s) / 12,T_(s)) P2 P12 P12 P10 P3 P11 P7 P9 P3 P1 P5P9 P4 P6 P6 P8

TABLE 2 VS₁ VS₂ VS₃ VS₄ VS₅ VS₆ VS₇ VS₈ VS₉ VS₁₀ VS₁₁ VS₁₂ VS₁₃ VS₁₄VS₁₅ VS₁₆ s₁ (t) 1  1  1  1  1  1  1  1 −1 −1 −1 −1 −1 −1 −1 −1 s₂ (t) 1 1 −1 −1  1  1 −1 −1  1  1 −1 −1  1  1 −1 −1 s₃ (t) 1  1  1  1 −1 −1 −1−1  1  1  1  1 −1 −1 −1 −1 s₄ (t) 1 −1  1 −1  1 −1  1 −1  1 −1  1 −1  1−1  1 −1 t′ = t mod T_(s) t′ θ [0,T_(s) / 12) P1 P12 P12 P11 P3 P4 P2 P9P3 P8 P10 P9 P5 P6 P6 P7 [T_(s) / 12, 2T_(s) / 12) P1 P12 P12 P11 P3 P4P2 P3 P9 P8 P10 P9 P5 P6 P6 P7 [2T_(s) / 12, 3T_(s) / 12) P1 P6 P12 P11P3 P4 P2 P3 P9 P8 P10 P9 P5 P6 P12 P7 [3T_(s) / 12, 4T_(s) / 12) P7 P6P12 P5 P3 P4 P2 P3 P9 P8 P10 P9 P11 P6 P12 P1 [4T_(s) / 12, 5T_(s) / 12)P7 P6 P6 P5 P3 P4 P2 P3 P9 P8 P10 P9 P11 P12 P12 P1 [5T_(s) / 12, 6T_(s)/ 12) P7 P6 P6 P5 P9 P4 P2 P3 P9 P8 P10 P3 P11 P12 P12 P1 [6T_(s) / 12,7T_(s) / 12) P7 P6 P6 P5 P9 P10 P8 P3 P9 P2 P4 P3 P11 P12 P12 P1 [7T_(s)/ 12, 8T_(s) / 12) P7 P6 P6 P5 P9 P10 P8 P9 P3 P2 P4 P3 P11 P12 P12 P1[8T_(s) / 12,9T_(s) / 12) P7 P12 P6 P5 P9 P10 P8 P9 P3 P2 P4 P3 P11 P12P6 P1 [9T_(s) / 12,10T_(s) / 12) P1 P12 P6 P11 P9 P10 P8 P9 P3 P2 P4 P3P5 P12 P6 P7 [10T_(s) / 12,11T_(s) / 12) P1 P12 P12 P11 P9 P10 P8 P9 P3P2 P4 P3 P5 P6 P6 P7 [11T_(s) / 12,T_(s)) P1 P12 P12 P11 P3 P10 P8 P9 P3P2 P4 P9 P5 P6 P6 P7

wherein VS_(i), i=1, 2, 3 . . . , 16 stands for 16 states of valuecombination of the four baseband spreading signals s₁(t), s₂(t), s₃(t),s₄(t); P_(K), K=1, 2, 3 . . . , 12 stands for value of the additionalphase θ, where ${P_{K} = {P_{1} + \frac{k\; \pi}{6}}},$  and P₁ is anyphase in [0,2π].
 7. A constant envelope multiplexed signal generated bythe method or the device for generating the dual-frequency constantenvelope multiplexed signal with four spreading signals as claimed inany preceding claim.
 8. An apparatus comprising means adapted to processa constant envelope multiplexed signal generated by the method or thedevice for generating the dual-frequency constant envelope multiplexedsignal with four spreading signals as claimed in any preceding claim. 9.A constant envelope multiplexed signal receiving device to receive theconstant envelope multiplexed signal generated by the method or thedevice for generating the dual-frequency constant envelope multiplexedsignal with four spreading signals as claimed in any preceding claim.10. A signal receiving device to receive the constant envelopemultiplexed signal as claimed in any preceding claim, or the constantenvelope multiplexed signal generated by the method or the device forgenerating the dual-frequency constant envelope multiplexed signal withfour spreading signals as claimed in any preceding claim, whichcomprises: a receiving unit for receiving the constant envelopemultiplexed signal; a demodulation unit for demodulating a signalcomponent modulated on the frequency f₁ of the received constantenvelope multiplexed signal, and for demodulating a signal componentmodulated on the frequency f₂ of the received constant envelopemultiplexed signal; and a processing unit for obtaining basebandspreading signals s₁(t) and s₂(t) based on the demodulated signalcomponent which is modulated on the frequency f₁, and for obtainingbaseband spreading signals s₃(t) and s₄(t) based on the demodulatedsignal component which is modulated on the frequency f₂.
 11. A signalreceiving method for receiving the constant envelope multiplexed signalas claimed in any preceding claim, or the constant envelope multiplexedsignal generated by the method or the device for generating thedual-frequency constant envelope multiplexed signal with four spreadingsignals as claimed in any preceding claim, which comprises: receivingthe constant envelope multiplexed signal; demodulating a signalcomponent modulated on the frequency f₁ of the received constantenvelope multiplexed signal, and for demodulating a signal componentmodulated on the frequency f₂ of the received constant envelopemultiplexed signal; and obtaining baseband spreading signals s₁(t) ands₂(t) based on the demodulated signal component which is modulated onthe frequency f₁, and for obtaining baseband spreading signals s₃(t) ands₄(t) based on the demodulated signal component which is modulated onthe frequency f₂.
 12. A signal receiving device to receive the constantenvelope multiplexed signal as claimed in any preceding claim, or theconstant envelope multiplexed signal generated by the method or thedevice for generating the dual-frequency constant envelope multiplexedsignal with four spreading signals as claimed in any preceding claim,wherein the additional phase lookup table is stored in the signalreceiving device and the signal receiving device comprises: a receivingunit for receiving the constant envelope multiplexed signal; ademodulation unit for demodulating the received constant envelopemultiplexed signal with a central frequency of f_(p)=(f₁+f₂)/2 so as toobtain the demodulated baseband signal; an additional phase looking upunit for obtaining, based on the additional phase lookup table, anadditional phase θ corresponding to each state among states of valuecombination of the four baseband spreading signals s₁(t), s₂, s₃, s₄; alocal replica generating unit for generating, based on the obtainedadditional phase θ, a local replica Í_(i)(t) of an in-phase basebandsignal and a local replica {tilde over (Q)}_(i)(t) of a quadrature-phasebaseband signal corresponding to each state; and a calculating unit forcalculating a correlation between the generated Ĩ_(i)(t) and {tilde over(Q)}_(i)(t) corresponding to each state with the demodulated basebandsignal, to determine the baseband spreading signals s₁(t), s₂(t), s₃(t),s₄(t) of the demodulated baseband signal, so as to achieve theacquisition and tracking of the constant envelope multiplexed signal.13. A signal receiving method for receiving the constant envelopemultiplexed signal as claimed in any preceding claim, or the constantenvelope multiplexed signal generated by the method or the device forgenerating the dual-frequency constant envelope multiplexed signal withfour spreading signals as claimed in any preceding claim, wherein thesignal receiving method comprises: storing the additional phase lookuptable; receiving the constant envelope multiplexed signal; demodulatingthe received constant envelope multiplexed signal through a centralfrequency of f_(p)=(f₁+f₂)/2 to obtain the demodulated baseband signal;obtaining, based on the additional phase lookup table, an additionalphase θ corresponding to each state among states of value combination ofthe four baseband spreading signals s₁(t), s₂(t), s₃(t), s₄(t);generating, based on the obtained additional phase θ, a local replicaĨ_(i)(t) of an in-phase baseband signal and a local replica {tilde over(Q)}_(i)(t) of a quadrature-phase baseband signal corresponding to eachstate; calculating a correlation between the generated Ĩ_(i)(t) and{tilde over (Q)}_(i)(t) corresponding to each state with the demodulatedbaseband signal, to determine the baseband spreading signals s₁(t),s₂(t), s₃(t), s₄(t) of the demodulated baseband signal, so as to achievethe acquisition and tracking of the constant envelope multiplexedsignal.
 14. A signal receiving device to receive the constant envelopemultiplexed signal as claimed in any preceding claim, or the constantenvelope multiplexed signal generated by the method or the device forgenerating the dual-frequency constant envelope multiplexed signal withfour spreading signals as claimed in any preceding claim, wherein theadditional phase lookup table is stored in the signal receiving deviceand the signal receiving device comprises: a receiving unit forreceiving, filtering and amplifying the constant envelope multiplexedsignal, wherein a central frequency of the filtering and amplifying isset at (f₁+f₂)/2; a demodulation unit for converting a carrier frequencyof the signal component to be processed to a corresponding intermediatefrequency, converting the signal component from analog to digital bysampling and quantizing the signal, and obtaining a receiver in-phasebaseband signal SI(t) and a receiver quadrature-phase baseband signal SQ(t) by multiplying the converted digital intermediate frequency signalby an in-phase carrier and a quadrature-phase carrier respectively; anadditional phase looking up unit for generating a spreading sequence offour baseband spreading signals with spreading chip waveform assignment,and generating, based on all the possible value combinations of thebinary baseband local signal replica of the four baseband spreadingsignals, an in-phase baseband signal local replica Ĩ_(i)(t) and aquadrature-phase baseband signal local replica {tilde over (Q)}_(i)(t)corresponding to each combination in the additional phase looking upunit, at each epoch, wherein the number of value combinations is denotedas g, g=2^(N), where there are N data channels, and for a special caseS_(i)={{tilde over (s)}₁, {tilde over (s)}₂, {tilde over (s)}₃, {tildeover (s)}₄} among the g value combinations, the generating rule ofĨ_(i)(t) and {tilde over (Q)}_(i)(t) is same as the transmitting device,and for obtaining the additional phase of the current time by looking upthe additional phase lookup table; a local replica generating unit forgenerating the in-phase baseband signal local replica Ĩ_(i)(t) and thequadrature-phase baseband signal local replica {tilde over (Q)}_(i)(t),whereĨ _(i)(t)=cos(θ_(i)){tilde over (Q)} _(i)(t)=sin(θ_(i)); and a calculating unit forobtaining the i-th (i=1, 2, . . . , g) group of a first in-phasecorrelation value corr1I_(i) and a first quadrature-phase correlationvalue corr1Q_(i) by multiplying the i-th (i=1, 2, . . . , g) group ofthe in-phase baseband signal local replica Ĩ_(i)(t) with the in-phasebaseband signal SI(t) and the quadrature-phase baseband signal SQ(t) andsending the multiplying results into an integration and dumping filterfor coherent integration with duration of TI, and for obtaining the i-th(i=1, 2, . . . , g) group of the second in-phase correlation valuecorr2I_(i) and the quadrature-phase correlation value corr2Q_(i) bymultiplying each group of the quadrature-phase baseband signal localreplica {tilde over (Q)}_(i)(t) with the in-phase baseband signal SI(t)and the quadrature-phase baseband signal SQ(t) and sending themultiplying results into the integration and dumping filter for thecoherent integration with duration of TI; for obtaining the i-th (i=1,2, . . . , g) group of in-phase combination correlation value I′_(i) andthe quadrature-phase combination correlation value Q′_(i) by combiningthe first in-phase correlation value corr1I_(i) and the firstquadrature-phase correlation value corr1Q_(i) of the i-th group with thesecond in-phase correlation value corr2I_(i) and the secondquadrature-phase correlation value corr2Q_(i) of the i-th group as:$\left\{ {\begin{matrix}{I_{i}^{\prime} = {{{corr}\; 2I_{i}} + {{corr}\; 1\; Q_{i}}}} \\{Q_{i}^{\prime} = {{{corr}\; 1I_{i}} - {{corr}\; 2Q_{i}}}}\end{matrix};} \right.$  and for selecting an optimal in-phasecombination correlation value I′ and an optimal quadrature-phasecombination correlation value Q′ to be a group of in-phase combinationcorrelation value I_(i)′ and quadrature-phase combination correlationvalue Q_(i)′, the value √{square root over (I′_(i) ²+Q′_(i) ²)} of whichis the maximum among all the groups, so as to determine the basebandspreading signal s₁(t), s₂(t), s₃(t), s₄(t), and to process I′ and Q′through traditional acquisition method and tracking loop.
 15. A signalreceiving method for receiving the constant envelope multiplexed signalas claimed in any preceding claim, or the constant envelope multiplexedsignal generated by the method or the device for generating thedual-frequency constant envelope multiplexed signal with four spreadingsignals as claimed in any preceding claim, wherein the signal receivingmethod comprises: storing the mentioned additional phase lookup table;receiving, filtering and amplifying the constant envelope multiplexedsignal, wherein a central frequency of the filtering and amplifying isset at (f₁+f₂)/2; converting a carrier frequency of the signal componentto be processed to a corresponding intermediate frequency, andconverting the signal component from analog to digital by sampling andquantizing the signal, and obtaining a receiver in-phase baseband signalSI(t) and a receiver quadrature-phase baseband signal SQ(t) bymultiplying the converted digital intermediate frequency signal by anin-phase carrier and a quadrature-phase carrier respectively; generatinga spreading sequence of four baseband spreading signals with spreadingchip waveform assignment, and generating, based on all the possiblevalue combinations of the binary baseband local signal replica of thefour baseband spreading signals, an in-phase baseband signal localreplica Ĩ_(i)(t) and a quadrature-phase baseband signal local replica{tilde over (Q)}_(i)(t) corresponding to each combination, at eachepoch, wherein the number of value combinations is denoted as g,g=2^(N), where there are N data channels, and for a special caseS_(i)={{tilde over (s)}₁, {tilde over (s)}₂, {tilde over (s)}₃, {tildeover (s)}₄} among the g value combinations, the generating rule ofĨ_(i)(t) and {tilde over (Q)}_(i)(t) is same as the transmitting device,and for obtaining the additional phase θ_(i) of the current time bylooking up the additional phase lookup table; generating the in-phasebaseband signal local replica Ĩ_(i)(t) and the quadrature-phase basebandsignal local replica {tilde over (Q)}_(i)(t), whereĨ _(i)(t)=cos(θ_(i)){tilde over (Q)} _(i)(t)=sin(θ_(i)); and obtaining the i-th (i=1, 2, . .. , g) group of a first in-phase correlation value corr1I_(i) and afirst quadrature-phase correlation value corr1Q_(i) by multiplying thei-th (i=1, 2, . . . , g) group of the in-phase baseband signal localreplica Ĩ_(i)(t) with the in-phase baseband signal SI(t) and thequadrature-phase baseband signal SQ(t) and sending the multiplyingresults into an integration and dumping filter for coherent integrationwith duration of TI, and for obtaining the i-th (i=1, 2, . . . , g)group of the second in-phase correlation value corr2I_(i) and thequadrature-phase correlation value corr2Q_(i) by multiplying each groupof the quadrature-phase baseband signal local replica {tilde over(Q)}_(i)(t) with the in-phase baseband signal SI(t) and thequadrature-phase baseband signal SQ(t) and sending the multiplyingresults into the integration and dumping filter for the coherentintegration with duration of TI; obtaining the i-th (i=1, 2, . . . , g)group of in-phase combination correlation value I′_(i) and thequadrature-phase combination correlation value Q′_(i) by combining thefirst in-phase correlation value corr1I_(i) and the firstquadrature-phase correlation value corr1Q_(i) of the i-th group with thesecond in-phase correlation value corr2I_(i) and the secondquadrature-phase correlation value corr2Q_(i) of the i-th group as:$\left\{ {\begin{matrix}{I_{i}^{\prime} = {{{corr}\; 2I_{i}} + {{corr}\; 1\; Q_{i}}}} \\{Q_{i}^{\prime} = {{{corr}\; 1I_{i}} - {{corr}\; 2Q_{i}}}}\end{matrix};} \right.$  and selecting an optimal in-phase combinationcorrelation value I′ and an optimal quadrature-phase combinationcorrelation value Q′ to be a group of in-phase combination correlationvalue I_(i)′ and quadrature-phase combination correlation value Q_(i)′,the value √{square root over (I′_(i) ²+Q′_(i) ²)} of which is themaximum among all the groups, so as to determine the baseband spreadingsignal s₁(t), s₂(t), s₃(t), s₄(t), and to process I′ and Q′ throughtraditional acquisition method and tracking loop.
 16. A programcomprising executable instructions to implement the method, device,apparatus in any preceding claim, or to generate a signal in anypreceding claim.
 17. A machine-readable storage for storing a program asclaimed in claim 16.